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A. E. LUNDELL. TELEPHONE EXCHANGE SYSTEM.

APPLICATION HLED DEC. 29,1916.

Patented June 17, 1919.

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y 1 WIM A y UNITED STATES PATENT GFFIQE.

ALBEN E. LUNDELL, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRICCOMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHAN GE SYSTEM.

Specification of Letters Patent.

Patented June 17, 1919.

To (all whom it may concern:

Be it known that I, ALBEN E. LUNDELL, a citizen of the United States,residing at New York, in the county of Bronx and State of New York, haveinvented certain new and useful Improvements in Telephone- Excha-ngeSystems, of which the following is a full, clear, concise, and exactdescription.

This invention relates to telephone exchange systems, and moreparticularly to automatic telephone exchanges in which automaticswitching devices are used for establishing connections between twolines, such as calling lines and trunk lines.

Automatic switching devices of the above defined type operate either asfinder or as trunk-hunting switches, 2'. 0., the movable contacts ofsuch switches serve as terminals for one line (for instance, the callingline), and the stationary contacts as terminals of the other line (forinstance, the trunk line), or vice versa. Upon thesuccessful operationof the automatic switch, the line seized by the movable contacts must beguarded against seizure by other automatic switching devices, meansbeing provided in association with such switching devices for preventingthe seizure of busy lines. Furthermore, means must be provided forcontrolling the exact centering of the movable contacts on the selectedstationary contacts. Itihas been the practice to provide automaticswitching devices in which, in addition to the movable contacts by whichthe conductors forming part of the talking circuit may be extended, twomovable contacts are provided through which the testing and the guardingof the line to be extended may be controlled, respectively. In suchswitching devices, the testing means, such as a marginal test relay, maybe used also for controlling the centering of the movable contacts. Inorder to use a single movable contact for controlling the testing andguarding operations, it has been proposed to provide, in addition to thetest relay, another relay by which the centering of the movable contactsmay be controlled.

It is the object of the present invention to provide a telephone systemin which a single relay is in association with an automatic switchingdevice, by means. of which the above mentioned testing, guarding andcentering operations are eantrolled, the

ing and guarding operations of the switching device being controllablethrough a single movable contact of the device.

The drawing represents as much of an automatic exchange system as isnecessary for a full understanding of the present invention.

The line finder and connector switches indicated in the drawingmay besubstantially the same as those disclosed in patent to Craft andReynolds, No. 1,123,696, although obviously this invention is applicableto systems in which line finder and connector switches of a widelyvarying char acter are utilized, or to systems in which, instead of aline finder, a line switch is used for extending the calling line.

Sequence switches 5 and 62, shown in the drawing, may be and preferablyare similar to that shown in patent to Reynolds and Baldwin No.1,127,808. The numerals which appear adjacent the several sequenceswitch contacts represent the positions of the sequence switch at whichthe respective contacts are closed, except the numerals which appearadjacent the sequence switch contacts 6, 63, which represent thepositions in which these contacts are opened, and consequently. thepositions in which the sequence switches may stop. The sequence switchcontacts shown below the horizontal dotted line are controlled bysequence switch 5 and those above such line by sequence switch 62.

The connector switch may be controlled by any wellknown means forseizing calling terminals of the desired line, but preferably iscontrolled by means of a sending apparatus such as disclosed in patentto A. E. Lundell, No. 1,168,319. A full disclosure of connector circuitsarranged to control the testing and private branch exchange huntingoperations of the connector may be had from a patent of A. E. Lundell,No. 1,284,392, issued November 12, 1918.

A subscriber at station A desiring to ob tain a connection with asubscriber at station B removes his receiver from the switchhook,whereupon a line relay 1 is energized in the Well-known manner. Relay 1closes a circuit from ground through a resistance 2, the armature andfront contact and the winding of a start relay 3 common to a pluralityof subscribers lines, to ground. The start relay closes than a fromgroaml,

through its armature and front contact, a contact 4 and the power magnetof sequence switch 5, to grounded battery. Upon the closure of thiscircuit, the sequence switch is moved out of position 1 and under thecontrol of its master contact 6, into position 2. A circuit is thenclosed from ground, through the armature and back contact of relay 7,sequence switch contact 8, and the winding of a magnet 9, to groundedbattery. Magnet 9 attracts its armature 10 and presses thus a brush rod11 against a roller 12 constantly rotating in the direction indi catedby the arrow. l/Vipers 13, 14 and 15 and brushes 16 and17 carried on thebrush rod 11 are thus moved in an upward direction. The wipers arearranged to successively engage sets of terminals arranged in a terminalbank 18, while brush 16 is arranged to wipe over aninterrupter plate 19,and brush 17 to make contact with a conducting segment 20. \Vheneverbrush 16 engages a conducting portion of plate 19, a circuit is closedfrom ground, through brush 16, plate 19, sequence switch contact 21,conductor 22, and the right-hand winding of relay 7, to groundedbattery. The relay 7 is marginal and is so adjusted that it will notattract its armature unless both its windings are energized at the sametime. For this reason relay 7 will not be operated until wiper 13engages a test terminal 23 of the calling line, when a circuit is closedfrom ground, through the left-hand winding of relay 7, sequence switchcontact 24, wiper 13, terminal 23, winding of a cut-off relay 25, theright-hand armature and front contact of relay 1, and the winding of thestart relay 3, to grounded battery. Relay 25 becomes energized and opensthe circuit of relay 1, which in turn causes the dene'rgization ofrelays 3 and 7. The conducting segments of plate 19 are so arranged withrespect to the terminals of bank 18, that,'when the brush 16engages aconducting segment, the line finder wipers are centered upon a set ofterminals. Thus relay 7 cannot be come energized until the wipers areproperly centered. The left-hand winding of relay 7 will not beenergized while the wiper 13 is traveling over test terminals of idlelines or lines engaged in conversation, because the line relays of suchlines are not energized. Relay 7, upon energization, opens the circuitof the magnet 9, and the brush rod 11 is thus arrested in its upwardmovement and held there by a pawl 55. Furthermore, relay 7, upon itsenergization, closes a circuit from ground, through its armature andfront contact, a contact 26 and the power magnet of sequence switch 5,to grounded battery, for moving this sequence switch out of position'2into position 16. For this reason, upon the deenergization of relay 7, acircuit'through sequence switch contact 8 this circuit the potential onthe callingtest terminal, such as 74 of the line leading to station A,is reduced, so as to prevent the seizure of this line by a connector, aswill be hereinafter set forth.

The calling line is then extended through wipers 14 and 15 and sequenceswitch contacts 33 and 34, to a trunk which may then be further extendedby automatic or manual means to the called subscribers station B.

After the completion of the conversation, the operator actuates key 29,and thus closes a circuit from grounded battery 35, through the windingof a marginal relay 36, key 29, sequence switch contact 27, wiper l3,terminal 23, and the windings of a marginal relay 37, to ground. Relay37 becomes energized and closes a shunt around its left-hand winding,whereupon the marginal relay 36 is permitted to operate for actuatingsignal 38 which indicates to the operator that relay 37 has beenactuated. Relay 37 controls operation of thecalling subscribers meter40. When battery is connected to the relay 37 through resistance 30 andcontact 28 of key 29, the relay does not operate, because current of ahigher voltage supplied by battery 35 is required for this purpose.

The operator then actuates key 50 and closes a circuit through a contact51 for moving the sequence switch out of position 16 into position 17. Acircuit is then closed from grounded battery, through the winding of amagnet 52 and a sequence switch contact 53, to ground. Magnet-52attracts its armature 54 and causes thus a pawl 55 to disengage the rod11. The armature 54 presses the brush rod against a roller 56,constantly rotating in the direction indi cated by the arrow, wherebythe wipers and brushes are restored to their normal position. a

When brush 17 engages plate 20, a ground is connectedthrough conductor57 and contact 58 'formoving the sequence switch into its normalposition 1, whereupon magnet 52 and relays 36, 37 and 25 becomedeenergized. All the apparatus is restored now to normal and is ready toreceive a new call.

The line leading to the station A is one of a plurality of lines leadingto a private branch exchange. If it is'desired to seize thifs line bymeans of'a connector, then the operator, or subscriber controlling theestablisliinent of the connection from a calling substation to thedesired station A causes, in the well-known manner, the energization ofa line relay 60 associated with such connector. The line relay closes acircuit from ground, through its armature and front contact, a contact61 and the power magnet of sequence switch 62 associated with theconnector, to grounded battery. Under the control of its normal contact63, the sequence switch is moved into position 2. A circuit is thenclosed from ground, through the armature and front contact of relay 60,sequence switch contact 64, and

the winding of a magnet 65, to grounded battery. Under the control ofmagnet 65, the wipers 66, 67 and 68 are caused to move a distancedetermined by the tens digits of the number designating the desiredline. After the. connector has been set in accordance with the tensdigit, relay 60 is caused to release its armature and closes thus acircuit from ground, through a contact 69 and the power magnet ofsequence switch 62, to grounded battery, for moving the sequence switchout of position 2 and into position 3. The magnet 65 is then momentarilydeenergized, but as soon as the relay 60 is again caused to operate andclose a circuit through sequence switch contact 61 for moving thesequence switch 62 out of position 3 and into position 4, the updrivemagnet is again operated, due to the reclosure of its above tracedcircuit, and causes the connector wipers to travel in accordance withthe units digit of the called subscribers number.

After the termination of the units impulses, relay 60 again becomesdeenergized and closes a circuit through sequence switch contact 69, fordriving the sequence switch 62 out of position 4 and into position 7. A

' circuit is now closed from ground, through a sequence switch contact70, and the righthand winding of a test relay 71, to grounded battery.Relay 71 closes a circuit from ground, through its right-hand armatureand front contact, and a contact 72, and the power magnet of thesequence switch 62, to grounded battery, for drivin this sequence switchout of position 7 an into position 9. Relay 71 connects ground, throughthe winding of a marginal relay 73, its lefthand winding, front contactand armature, and test wiper 68 of the connector, to the calling testterminal 74 of the called line.

If the line leading to station A has been seizedby the line finder,grounded battery is connected through resistance 30, key 29, sequenceswitch contact 27, line finder wiper 13, and the answering test terminal23, to the callin test terminal 74. The test terminal 74 is a soconnected through the winding of a cut-off relay 25 and resistance 2 toground. Due to the fact that the shunt closed through the cubofl relay25 and resistance 2 is of relatively low resistance with respect to theshunt closed through the line finder wiper 13, the relay 73 which ismarginal in operation, will not operate; relay 71, however, willmaintain its armatures attracted under the control of its left-handwinding. A circuit is therefore closed from grounded battery, throughwinding of magnet 65, the back contact and armature of relay 73,sequence switch contact 80, and the 75 right-hand front contact andarmature of relay 71, to ground. The magnet 65 operates the connectorwipers to hunt for an idle line leading to the desired private branchexchange.

The connector switch continues to hunt 1 until relay 71 becomesdeenergized. This relay 71 will become denergized as soon as an idleline is encountered, that is to say, a line to the multiple calling testterminals of which no battery is connected through the test wiper of aline finder or connector switch. When the test relay 71 becomesdeenergized, it breaks at its front contact the energizing circuit ofmagnet 65 and closes a circuit from ground, through the righthandarmature and back contact of relay 71, a contact 81 and the power magnetof sequence switch 62, to grounded battery, for moving this sequenceswitch out of position 9 into position 15. From positions 8 to 15 of thesequence switch, contact 82 is closed, and thus grounded battery isconnected through a resistance 83 and the left-hand back contact andarmature of relay 71 to the multiples of a calling test terminal, whichwill render the line busy in the same manner as it is rendered busy dueto the shunt closed through the test wiper 13 of the line finder." Inposition 15, contacts 84 and 85 of the sequence switch are also closedand the talking conductors extended to the called line A. The line maynow be signaled by any well-known means, a

In the lower left-hand corner of the drawing, it is shown how the testconductor of a direct line is connected to the calling and answeringtest terminals. The ,reference characters used in connection with thisshowing are the same as in connection with the private branch exchangeline, with the exception that each reference character is primed. Itwill be seen that the test terminals are not connected direct to thewinding of the cut-off relay 25', but through the windings of relay 37.In the same manner as above described, the relay 37 will not operatewhen battery is connected through resistance 30 and line finder wiper 13to its winding, but only when the operator 12 actuates the meter key 29and connects the metering battery 35 to its winding. The operation ofthe line finder in seizing such a direct line will be the same also inother respects as above described in connection with a private brancheXchange. Due to the fact,-however, that the shunt closed from groundthrough resistance 2, the winding of relay 25, the windings of relay 37,to test terminal 74, is of a relatively high resistance with respect tothe shunt closed through the test wiper of a connector or line finderwhen the wiper 68 of the connector is caused to engage terminal 74,relay 73 will be energized even if the terminal 74 tests busy. Relay 71being energized at this time, a circuit is closed from ground, throughthe right-hand armature and front contact of this relay, sequence switchcontact 80, the armature, and front contact of relay 73V and the windingof sequence switch 62, to grounded battery, and this sequence switch'ismoved out of position 9 into position 12. Relay 71 being energized, thesequence switch is maintained in position 12 for a sufiiciently longperiod to permit the release of the connector in any well-known manner.

If the desired direct line is idle, then relay 73 remain deenergized.The relay 71 becomes immediately deenergized and closes a circuit fromground, through its right-hand armature and back contact, a contact 81,and the power magnet of sequence switch 62, to grounded battery. Contact81 being closed also in position '12, the sequence switch will be movedthrough position 12 into position 15, which is the talking posi tion.The calling and called subscribers are interconnected by means of acircuit including wipers 66 and 67 of 'the connector and sequenceswitchcontacts 84 and 85.

What is claimed is:

1. In combination, a plurality of stationary. contacts, a movablecontact, means for operating said movable contact to engage any one ofsaid stationary contacts, means for rendering engaged stationarycontacts busy, a test relay having two windings, a circuit for one ofsaid windings including said movable contact, a c1rcu1t for for closingsaid last mentioned circuit depending on the distance said movablecontact has traveled with respect to a certain one of saidstationarycontacts, guarding means, means responsive to the actuation of saidrelay for operating said guarding means, and a circuit for saidoperating magnet controlled by said relay.

3. In combination, a plurality of stationary contacts, a movablecontact, a normally ineffective guarding means for said stationarycontacts, a marginal test relay having two windings, a circuit for oneof said windings. including said movable contact, operating means forsaid movable contact controlled by said relay for operating said movablecontact to move into association with any one of said stationarycontacts, a circuit for the other winding of said relay, means forclosing the last mentioned circuit depending. on the distance traversedby .said movable contact with respect to one of said stationarycont-acts, said relay being energized only in response to thesimultaneous closure of both said circuits, and means operable upon theenergization of said relay for rendering said guarding means eflective.

. In witness whereof, I hereunto subscribe my name this 28th day ofDecember A. D., 1916.

' ALBEN E. LUNDELL.

Copies of this patent'may 'be obtained for five cents each,(byad'dressing the Commissioner of Patents, Washington, D. 0.

